Migration and generation of contaminants from launch through recovery: LDEF case history

The migration of contaminants to and between Long Duration Exposure Facility (LDEF) surfaces reveals new information relevant to all future space missions. The surface of the LDEF satellite closely paralleled over seven meters of the shuttle during one launch and one reentry. Transfer of contaminants from the shuttle bay to the payload were documented and partially quantified for both the launch and recovery separately. LDEF carried a load of volatile silicones and hydrocarbons into orbit which were then polymerized by UV radiation into tough, dark brown stains on exposed surfaces. The distribution of these stains is providing new information on deposition mechanisms that should be studied on future missions. Electrostatic effects, diffusional flow, and effects due to small surface temperature differences at the time of UV exposure are suggested. The types of functional groups present in the LDEF deposit it nearly identical to stains recovered from other spacecraft. These stains were remarkably stable in low Earth orbit even with atomic oxygen exposure if the amount of silicones present was sufficient to create a sealing layer of silicon dioxide over the dark brown stain beneath.